Generally, giant magneto-resistance (GMR) elements for detecting presence or absence of a magnetic field are widely known. The phenomenon that an electric resistance changes when a magnetic field is applied, is called magnetoresistance effect. Although the resistance change of a common substance would be several percent, the resistance change of such GMR elements reaches several tens of percent. For this reason, the GMR elements are widely used for recording heads of hard disks.
FIG. 1 is a perspective view illustrating the operation principle of the conventional GMR element, and FIG. 2 is a partial cross-sectional view of FIG. 1. In the drawings, reference numeral 1 denotes an antiferromagnetic layer, reference numeral 2 denotes a pinned layer (fixed layer), reference numeral 3 denotes a Cu layer (spacer layer), and reference numeral 4 denotes a free layer (free rotation layer). A magnetization direction of a magnetic material changes electronic spin scattering, and changes a resistance. In other words, the change of the resistance is represented by ΔR=(RAP−RP)×RP (where RAP is a resistance when magnetization directions on upper and lower sides are not parallel, and RP is a resistance when the magnetization directions on upper and lower sides are parallel).
As for the magnetic moment of the pinned layer 2, the direction is fixed by magnetic coupling with the antiferromagnetic layer 1. When the direction of the magnetic moment of the free rotation layer 4 changes due to leakage field, a resistance applied on the current flowing through the Cu layer 3 changes, and a change of the leakage field can be detected.
FIG. 3 is a configuration diagram illustrating a stack structure of the conventional GMR element. In the drawing, reference numeral 11 denotes an insulating film, reference numeral 12 denotes a free layer (free rotation layer), reference numeral 13 denotes a conductive layer, reference numeral 14 denotes a pinned layer (fixed layer), reference numeral 15 denotes an antiferromagnetic layer, and reference numeral 16 denotes an insulating film. The free layer (free rotation layer) 12 is a layer in which a magnetization direction rotates freely, and is made of NiFe or CoFe/NiFe. The conductive layer 13 is a layer in which a current flows and the electrons are scattered dependent on their spin, and is made of Cu. The pinned layer (fixed layer) 14 is a layer in which a magnetization direction is fixed in a specific direction, and is made of CoFe or CoFe/Ru/CoFe. The antiferromagnetic layer 15 is a layer for fixing the magnetization direction of the pinned layer 14, and is made of PtMn or IrMn. The insulating films 11 and 16 are made of Ta, Cr, NiFeCr, or AlO. It is to be noted that the pinned layer 14 may use a self-bias structure instead of the antiferromagnetic layer.
PTL 1, for example, describes a magnetic sensor including magnetoresistance effect elements and a soft magnetic material provided at a position where it does not come into contact with each of the magnetoresistance effect elements through an insulating layer. In the magnetic sensor, the magnetoresistance effect elements are arranged at both sides of the soft magnetic material in a first horizontal direction in plan view such that fixed magnetization directions of fixed magnetic layers thereof are directed in the first horizontal direction. And the fixed magnetization directions of the magnetoresistance effect elements arranged at both sides of the soft magnetic material are set to be opposite to each other, or the fixed magnetization directions of the magnetoresistance effect elements arranged at the same side of the soft magnetic material are set to be opposite to each other.